Phosphoric Acid Quenched Creping Adhesive

ABSTRACT

An improved creping adhesive is prepared by first reacting a dibasic carboxylic acid, or its ester, half-ester, or anhydride derivative, with a polyalkylene polyamine, preferably in aqueous solution, under conditions suitable to produce a water soluble polyamide. The water-soluble polyamide is then reacted with an epihalohydrin until substantially fully cross-linked, and stabilized by acidification with phosphoric acid at the end of the polymerization reaction to form a water-soluble poly(aminoamide)-epihalohydrin creping adhesive that is re-wetable and facilitates water spray removal of buildup so as to lengthen the life of the creping blades, with attendant significant decrease in downtime and maintenance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of prior U.S. patent application Ser. No.11/081,387, filed Mar. 15, 2005, the priority of which is hereby claimedand its disclosure incorporated by reference in its entirety.

FIELD OF INVENTION

The invention is in the field of polyamide-epihalohydrin crepingadhesives.

BACKGROUND OF THE INVENTION

In the manufacture of tissue and towel products, a common step iscreping the product to provide desired aesthetic and performanceproperties to the product. Creping is commonly used in both theconventional wet press and through air drying processes. Many of theaesthetic properties of tissue and towel products rely more upon theperceptions of the consumer than on properties that can be measuredquantitatively. Such things as softness, and perceived bulk are noteasily quantified, but have significant impacts on consumer acceptance.However both softness and bulk are dramatically improved by the crepingprocess. Creping is generally accomplished by mechanicallyforeshortening or compacting paper in the machine direction with aflexible blade, a so-called doctor blade, against a Yankee dryer in anon-machine operation. This blade is also sometimes referred to as acreping blade or simply a creper. By breaking a significant number ofinterfiber bonds and slowing down the speeds between the Yankee and thereel, creping increases the basis weight (mass per unit area) of thepaper and effects significant changes in many physical properties,particularly when measured in the machine direction. Creping thusenhances bulk and stretch, and increases the perceived softness of theresulting product.

A Yankee dryer is a large diameter, generally 8-20 foot drum which isdesigned to be pressurized with steam to provide a hot surface forcompleting the drying of papermaking webs at the end of the papermakingprocess. The paper web which is first formed on a foraminiferous formingcarrier, such as a Fourdrinier wire, where it is freed of the copiouswater needed to disperse the fibrous slurry, then is usually transferredto a felt or fabric either for dewatering in a press section wherede-watering is continued by mechanically compacting the paper or by someother water removal method such as through-drying with hot air, beforefinally being transferred in the semi-dry condition to the surface ofthe Yankee for the drying to be completed. Before transferring to theYankee dryer, an adhesive is applied directly to the Yankee dryer.

Obtaining and maintaining adhesion of tissue and towel products toYankee dryers is an important factor in determining crepe quality.Re-wetability, doctorability, and the level of adhesion are importantproperties of a creping adhesive. The ability of the adhesive to berewet on the surface of the dryer helps to prevent buildup on the drumand on the creping blade. Inadequate adhesion results in poor creping,sheet floating, and poor sheet handling whereas excessive adhesion mayresult in crepe blade picking, sheet plugging behind the crepe blade,and sheet breaks due to excessive tension. Traditionally, crepingadhesives alone or in combination with release agents and/or modifiershave been applied to the surface of the dryer in order to provide theappropriate adhesion to produce the desired crepe. The adhesive coatingalso serves the purpose of protecting the Yankee dryer and creping bladesurfaces from excessive wear. In this role, the coating agents provideimproved runnability of the tissue machine. As creping blades wear, theymust be replaced with new ones. This replacement process represents asignificant source of tissue machine downtime, or lost production.

Various types of creping adhesives have been used to adhere fibrous websto dryer surfaces such as Yankee dryers. Some examples of prior artcreping adhesives rely upon combinations of self-crosslinkable softpolymers with a non-film forming hard polymer emulsion (U.S. Pat. No.4,886,579). Some others involve thermoset resins (U.S. Pat. Nos.4,528,316 and 4,501,640). The ability to control the mechanicalproperties of the polymers, as well as the adhesion and release of thefibrous web from the Yankee dryer, is limited when using these types ofcreping adhesives. A variety of proposals have been made in an attemptto improve the properties of certain adhesives. For example, U.S. Pat.No. 5,370,773 describes the use of a phosphate surfactant with anadhesive composition that includes a non-self-crosslinkable polymer oroligomer having functional groups that can be ionic crosslinked using ahigh valence metallic crosslinking agent. U.S. Pat. No. 6,280,571describes the use of an acid selected from hypophosphorous acid,phosphorous acid, hypodiphosphoric acid, diphosphorous acid,hypophosphoric acid, pyrophosphorous acid, or their salts, to stabilizea polymer selected from polyamidoamine-epichlorohydrin resin,polyamine-epichlorohydrin resin, reaction products of epichlorohydrinwith highly branched polyamidoamines and polyvinyl alcohol.

Poly(aminoamide)-epihalohydrin type creping adhesives (also referred toas PAE resins), exemplified by poly(aminoamide)-epichlorohydrin, providea class of resins distinct from the above polymers. Resins of this typehave been used for many years in paper making and are described in U.S.Pat. Nos. 2,926,116 and 3,058,873, the disclosure of which areincorporated herein by reference. They are generally prepared byreacting an epihalohydrin and a polyamide containing secondary ortertiary amine groups, followed by stabilizing the reaction products byacidification with sulfuric or hydrochloric acid. They have very usefulproperties when freshly applied in runnability and initial re-wetabilityand doctorability. However, a problem with thepoly(aminoamide)-epihalohydrin type creping adhesives is the phenomenonof coating buildup. This problem is evidenced by high spots in thecoating on the Yankee and/or build up on the rear surface of the blade,particularly along the edges or corners of the creping blade, which cancause chattering, or bouncing of the blade. Ultimately, portions of thesheet may travel underneath the creping blade, causing picks or holes inthe sheet leading to sheet breaks and machine downtime. Commonly watersprays have been used to remove or minimize adhesive buildup, buteventually may prove inadequate.

In order to produce a bulky and soft tissue with conventional wet presspaper machines, the paper sheet is preferably dried to very low moisturelevels (e.g., less than 3%), thus economic considerations often requirean adhesive that will perform at very high sheet temperatures. But theforegoing problems with the poly(aminoamide)-epihalohydrin type crepingadhesives can be particularly severe at higher temperatures.

Another difficulty with PAE resins is the adverse effect of sizingagents such as alkyl ketene dimer (AKD), alkylene ketene dimers andalkylene succinic anhydride (ASA) on the creping process. These sizingagents, particularly AKD, are sometimes added to paper webs to impartmoisture resistance properties for some special grades of paper.However, AKD performs as a strong release on the Yankee. When AKD isadded to the furnish in the wet end, most of the PAE adhesives haveissues in generating sufficient adhesion between the Yankee surface andthe sheet often resulting in poor creping and sheet handling issues orlimiting the amount of these sizing agents that can be incorporated intothe sheet if good creping is desired.

SUMMARY OF THE INVENTION

The present invention provides an improved method for manufacturingtissue using an improved poly(aminoamide)-epihalohydrin creping adhesivethat is re-wetable, and that reduces buildup, or facilitates itsremoval, with attendant significant decrease in downtime andmaintenance. Moreover, we have discovered that, in one particularlydemanding application, the creping adhesive of the present inventionprovides a particularly impressive improvement. When tissue substrates,such as might be used in napkin basestock, are treated with sizingagents such as AKD, they can become particularly difficult to crepe. Wehave found that the creping adhesives of the present invention providedramatically improved creping performance when used with AKD treatedbase sheets, such as are disclosed in U.S. application Ser. No.10/995,457 filed Nov. 22, 2004 entitled “Multi-Ply Paper Product WithMoisture Strike Through Resistance And Method Of Making The Same.”

The adhesive is prepared in the usual manner of preparingpoly(aminoamide)-epihalohydrin creping adhesives with a change in onestep, a change that appears to be simple, yet which, very surprisingly,results in essentially substantial alleviation of the problems ofadhesive buildup. This is accomplished at the end of the polymerizationreaction, at the quenching step, by replacing the usual sulfuric acid orhydrochloric acid with phosphoric acid.

More particularly, a poly(aminoamide)-epihalohydrin creping adhesive isprepared by first reacting a dibasic carboxylic acid, or its ester,half-ester, or anhydride derivative, with a polyalkylene polyamine,preferably in aqueous solution, under conditions suitable to produce awater soluble polyamide. The water-soluble polyamide is then reactedwith an epihalohydrin until substantially fully cross-linked, andstabilized by acidification with phosphoric acid at the end of thepolymerization reaction to form the water-soluble cationicpolyamide-epihalohydrin resin of this invention. The epihalohydrin usedin preparing the phosphoric acid stabilizedpoly(aminoamide)-epihalohydrin resin is preferably epichlorohydrin, toprepare a phosphoric acid stabilized poly(aminoamide)-epichlorohydrinresin.

The manufacturing method includes applying a creping adhesive to thesurface of a Yankee dryer, while using a felt or carrier fabric to applya preformed nascent fibrous paper web to the creping adhesive on thesurface of the dryer, thereafter removing the paper web from the Yankeedryer by use of a creping blade and winding the dried paper onto a roll.The method may optionally also include applying water or a modifier,e.g., by spraying, to the exposed edges of the Yankee drum directedprincipally against the drum surfaces not contacted by the felt orcarrier fabric, to control buildup.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a Yankee dryer to which a tissueweb is presented, dried, creped, and then wound into a soft roll;

FIG. 2 is a photograph showing the drive sides, left in the photograph,of two crepe blades run for about 80 minutes, with a sulfuric acidstabilized poly(aminoamide)-epichlorohydrin adhesive on the top blade inthe photograph, and with phosphoric acid stabilizedpoly(aminoamide)-epichlorohydrin adhesive of this invention on thebottom blade;

FIG. 3 is a photograph of the drive and operator sides, respectivelyleft and right sides in the photograph, of 3 blades run with thephosphoric acid stabilized poly(aminoamide)-epichlorohydrin adhesive ofthis invention, from top to bottom with sorbitol modifier at 5 wt. % ofadhesive solids, 10 wt. % of adhesive solids, and 20 wt. % of adhesivesolids for about 100 minutes each, the bottommost blade showing theeffect of water spray on the adhesive with sorbitol modifier at 10 wt. %of adhesive solids; and

FIG. 4 is a table showing a comparison of the physical properties tissueproduced using the phosphoric acid stabilized adhesive of this inventionas compared to tissue produced using the sulfuric acid stabilizedadhesive.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates steps in formation of a tissue paper web suitable foruse as a facial tissue. The method illustrated is a schematic exampleonly and is not meant to indicate or infer any limitations on themethod, but is only meant to illustrate the method in broad terms,representing one of a number of possible configurations used inprocessing tissue or towel products. The manufacturing method includesapplying a creping adhesive to the surface of a Yankee dryer, using afelt or carrier fabric to apply a preformed fibrous nascent web to thecreping adhesive on the surface of the dryer, drying the nascent web toform a paper web on the surface of the Yankee and, thereafter, removingthe paper web from the Yankee dryer by use of a creping blade andwinding the dried paper onto a roll. The method optionally also includesapplying water or modifier, e.g., by spraying, to exposed edges of theYankee drum, i.e., drum surfaces not contacted by the felt or carrierfabric.

In this particular arrangement, transfer and impression felt carrierfabric designated at 1 carries the nascent, dewatered paper web 2 aroundturning pressure roll 3 to the nip between the pressure roll 3 andYankee dryer drum 4. The fabric, web and dryer move in the directionsindicated by the arrows. The entry of the web to the dryer is wellaround the drum 4 from a creping doctor blade 5 which, as schematicallyindicated at 6, crepes the traveling web from the dryer. Creped web 7exiting from the dryer is wound into a soft creped tissue reel 8. Toadhere nascent web 2 to the surface of the dryer, spray boom 9 spraysadhesive 10 directly onto the outer surface of the internally heatedYankee drum 4. Additionally, hot air flow is applied to the adheredpaper web by a hood 11. Suitable apparatus for use with the presentinvention are disclosed in U.S. Pat. Nos. 4,304,625 and 4,064,213, whichare hereby incorporated by reference.

The apparatus can be configured so that the felt or carrier fabric 1 isof a dimension sufficient to entirely cover the surface of the drum 4contacted by the doctor blade 5. If it not so dimensioned, which istypically the case, then in accordance with a preferred embodiment ofthe invention, possible in substantial part by the superiorre-wetability of the adhesive obtained by the use of a phosphoric acidquenching step, water or modifier is applied to the exposed edge(s). Anedge spray 12 can be used to apply a water spray 13 to the exposed sideedge or edges of the drum, i.e., on the drive side and/or operator sideof the adhesive coated Yankee drum, as the case may be.

This illustration does not incorporate all the possible configurationsused in presenting a nascent web to a Yankee dryer. It is used only todescribe how the adhesive of the present invention can be used topromote adhesion and thereby influence the crepe of the product. Thepresent invention can be used with all other known processes that relyupon creping the web from a creping surface. In the same manner, themethod of application of the adhesive to the surface of the dryer or theweb is not restricted to spray applications, although these aregenerally the most expedient for adhesive application.

The present invention is useful for the preparation of fibrous webswhich are creped to increase the thickness of the web and to providetexture to the web. The invention is particularly useful in thepreparation of final products such as facial tissue, napkins, bathtissue, paper towels and the like. The fibrous web can be formed fromvarious types of wood pulp based fibers which are used to make the aboveproducts such as hardwood kraft fibers, softwood kraft fibers, hardwoodsulfite fibers, softwood sulfite fibers, high yield fibers such aschemi-thermo-mechanical pulps, thermomechanical pulps, or refinermechanical pulps and the like. Furnishes used may also contain or betotally comprised of recycled fibers (i.e., secondary fibers). Thefibrous web, prior to application to the Yankee dryer, usually has awater content of 40 to 80 wt. %, more preferably 50 to 70 wt. %. At thecreping stage, the fibrous web usually has a water content of less than7 wt. %, preferably less than 5 wt. %. The final product, after crepingand drying, has a basis weight of 7 to 80 pounds per ream.

The creping operation itself can be conducted under conventionalconditions except that the creping adhesive of the present invention issubstituted for a conventional creping adhesive.

In accordance with this invention, an improvedpoly(aminoamide)-epihalohydrin creping adhesive that is re-wetable andfacilitates water spray removal of buildup so as to lengthen the life ofthe creping blades, with attendant significant decrease in downtime andmaintenance. The adhesive is prepared in the usual manner of preparingpoly(aminoamide)-epihalohydrin creping adhesives with a change in onestep, a change that appears to be simple, yet which, very surprisingly,results in substantial alleviation of the problems of adhesive buildup;and, in many cases, makes it possible for the creping package to providean increased level of adhesion producing a softer more flexible crepedsheet as reflected by a decreased tensile modulus. This change isaccomplished at the end of the polymerization reaction, at the quenchingstep, by replacing the usual sulfuric acid or hydrochloric acid withphosphoric acid.

More particularly, a poly(aminoamide)-epihalohydrin creping adhesive isprepared by first reacting a dibasic carboxylic acid, or its ester,half-ester, or anhydride derivative, with a polyalkylene polyamine,preferably in aqueous solution, under conditions suitable to produce awater soluble polyamide. To form the water-soluble cationicpolyamide-epihalohydrin resin of this invention, the water-solublepolyamide is then reacted with an epihalohydrin, and stabilized byacidification with phosphoric acid at the end of the polymerizationreaction, preferably with 85% ortho-phosphoric acid, 0.1-2.0 molarequivalent based on polymer content to a pH of 3.5-7.0, most preferablyto 7.0. Acidification quenches the epihalohydrin cross-linking reaction,in which molecular weight is built, to prevent gelation. The acid saltsof the remaining amine groups in the polymer backbone are less reactivetoward the azetidinium rings than were the free amines at the higher pHbefore quenching.

The extent of cross-linking, whether partial or fully cross-linked, canbe controlled with reaction conditions. For fully cross-linked polymer,epihalohydrin is added in aliquots to base polymer and reacted at hightemperature at each stage until there is viscosity “burn-out”, with nomore advancement. The polymer is then acidified, ensuring that thedifunctional epihalohydrin has reacted completely with prepolymer. Thecorrect viscosity end point is determined by carefully controlling theamount of epihalohydrin added. For partial cross-linking, a small excessof epihalohydrin is added (compared to fully cross-linked, either inaliquots or at once) and reacted to a pre-determined viscosity end pointbefore the reaction burns out. The viscosity advancement is halted atthe determined end point by addition of acid. This ensures that theepihalohydrin is not completely cross-linked and that some residualpendant chlorohydrin remains.

We can distinguish differences in the degree of cross-linking with totaland ionic chloride titrations. C-13 NMR can detect pendant chlorohydrinpresent in partially cross-linked resins. Also, the viscosity of thepartially cross-linked material can be made to advance with heat, andcan change during storage while fully cross-linked materials are farmore stable over time.

The polyalkylene polyamine preferably has the repeating units

—NH(C_(n)H_(n)HN)_(x)—CORCO—

where n and x are each 2 or more and R is the divalent hydrocarbonradical of the dibasic carboxylic acid or its derivative containing fromabout 3-10 carbon atoms. The polyamide secondary amine groups arepreferably derived from a polyalkylene polyamine for examplepolyethylene polyamides, polypropylene polyamines or polybutylenepolyamines and the like, with diethylenetriamine being preferred.

Poly(aminoamide)-epihalohydrin resins undergo at least two types ofreactions that contribute to wet strength. One reaction involves thereaction of an azetidinium group in one molecule with an unreactedsecondary amine group in another molecule to produce a cross-linkbetween the two molecules. In the second reaction at least twoazetidinium groups on a single resin molecule react with carboxyl groupson two different fibers to produce an interfiber cross-link. It is alsoknown to utilize promoters such as carboxymethyl cellulose to enhancethe performance of these materials in paper products.

The dicarboxylic acid is one of the saturated aliphatic dibasiccarboxylic acids containing from about 3 to about 10 carbon atoms.Examples are malonic, succinic, glutaric, adipic, pimelic, suberic,azelaic, and sebacic dicarboxylic acids, and mixtures thereof. Examplesof ester, half-ester, or anhydride derivatives of adipoc acid aredimethyl adipate, diethyl adipate, adipic acid monomethyl ester, adipicacid monoethyl ester, and adipic acid anhydride. Corresponding esters,half esters, and anhydrides of each of the listed dibasic acids arefurther examples. Blends of two or more of derivatives of dibasiccarboxylic acids may also be used, as well as blends of one or morederivatives of dibasic carboxylic acids with dibasic acids. Dicarboxylicacids containing from 4 to 8 carbon atoms, and their derivatives, arepreferred, with adipic acid (hexanedioic acid) being most preferred.Preferably the mole ratio of polyalkylene to dibasic carboxylic acid, orequivalent amount of its derivative, is from about 0.8 to 1 to about 1.5to 1. The mole ratio of epihalohydrin to secondary amine groups in thepolyamide is preferably from about 0.01 to 1 to about 2 to 1.

The epihalohydrin used in preparing the poly(aminoamide)-epihalohydrinresin is preferably epichlorohydrin, to prepare a phosphoric acidstabilized poly(aminoamide)-epichlorohydrin resin.

Finally, as a last step, the poly(aminoamide)-epihalohydrin resin isstabilized by acidification to a pH of 3.5-7.0, preferably to 7.0, atthe end of the polymerization reaction. In accordance with thisinvention, in place of the usual acidification with sulfuric acid, or insome cases with hydrochloric acid, the poly(aminoamide)-epihalohydrinresin is stabilized with phoshoric acid. Preferably, it is stabilizedwith 85% ortho-phosphoric acid, 0.1-2.0 molar equivalent based onpolymer content phosphoric acid, to a pH of 3.5-7.0, most preferably to7.0.

The following Examples are illustrative of, but are not to be construedas limiting, the invention embodied therein.

Example 1 Synthesis of Polyamide Prepolymer

A 2.5 l (2.5 liter) reactor equipped with hot oil bath, stainless steelstirring shaft, agitator, thermometer and a reflux condenser withnitrogen inlet. The reactor condenser was configured for reflux.990.2242 grams of liquid DETA (diethylenetriamine) were loaded to thereactor at 25° C. and atmospheric pressure. To this was added 1446.0327grams of solid adipic acid over a 30 minute period in six equal portionswith agitation and at atmospheric pressure. The reaction was exothermal,raising the temperature from 40° C. to about 147° C. during the courseof adipic acid additions. After the adipic acid load was complete, thereactor condenser was switched from reflux to distillation and heat wasapplied to raise the reaction temperature to a maximum of 165° C. Waterbegan to distill from the reaction mixture at about 160° C., and heatwas supplied to slowly ramp-up the reaction temperature to a maximumtemperature of 165° C. Once the desired degree of polymerization wasobtained as determined by check-cut viscosity tests (i.e., comparing theviscosity of small samples taken during this polymerization to theviscosity of a sample having a known degree of polymerization obtainedduring a previous synthesis) the condenser was then switched back toreflux, and fresh water was gradually loaded to the molten prepolymer at158° C. and atmospheric pressure. The addition of water brought theprepolymer to about 66% concentration and reduced the reactiontemperature to about 100° C. The prepolymer was then diluted to 45%non-volatiles, and the viscosity was 290 cP by Brookfield.

Example 2 Synthesis of Phosphoric Acid Stabilized Crepe Adhesive

To a 5 l glass reactor equipped with stirring shaft, stainless steelcooling coils, heating mantle, reflux condenser, pH/temperature probe,and equal pressure addition funnel was added 3295.71 grams of polyamideprepolymer from Example 1. To this was added 1372.32 grams of water. Themixture was then heated to 40° C. 23.24 grams of epichlorohydrin wasadded via addition funnel to the heated mixture in 2 aliquots over a 2hour period. After addition of the first aliquot of epichlorohydrin thereaction was heated to 90° C. The viscosity of the mixture was monitoredwith Gardner-Holdt bubble tubes every ten minutes over the 2 hourperiod. The reaction mixture advanced to a maximum of GH Gardner-Holdtbubble tube viscosity. When the viscosity ceased to advance further withcontinuous heating at 90° C., the reaction mixture was cooled to 25° C.and 407 grams of 85% phosphoric acid was slowly added to adjust the pHof the mixture to 7.0. Water was added to dilute the finished polymermixture to 35% non-volatile content, with a Brookfield viscosity of 150cP and pH 7.0

Example 3 Synthesis of Prior Art Sulfuric Acid Stabilized Crepe Adhesive

To a 2.5 l glass reactor equipped with stirring shaft, stainless steelcooling coils, heating mantle, reflux condenser, pH/temperature probe,and equal pressure addition funnel was added 1647.86 grams of polyamideprepolymer from Example 1. To this was added 686.16 grams of water. Themixture was then heated to 40° C. 14.32 grams of epichlorohydrin, wasadded via addition funnel to the heated mixture in 3 aliquots over a 2hour period. After addition of the first aliquot of epichlorohydrin thereaction was heated to 90° C. The viscosity of the mixture was monitoredwith Gardner-Holdt bubble tubes every ten minutes over the 2 hourperiod. The reaction mixture advanced to a maximum of GGH Gardner-Holdtbubble tube viscosity. When the viscosity ceased to advance further withcontinuous heating at 90° C., the reaction mixture was cooled to 25° C.and 116.52 grams of 93% sulfuric acid was slowly added to adjust the pHof the mixture to 7.0. Water was added to dilute the finished polymermixture to 35% non-volatile content, with a Brookfield viscosity of 130cP and pH 7.0.

Physical Properties of the Adhesives

Physical properties of the formulations of Example 2 (denoted 378G55)and Example 3 (denoted 315D54), are shown in Table 1. The materials wereanalyzed for molecular weight based on poly(vinyl pyridine) standards.To determine weight % solids, weighed portions of each sample were driedfor 4 hours at 105° C. in a weighed aluminum pan. The dried samples werecooled and weighed again to determine water loss. For C-13 NMR analysis,2.8 ml of the adhesive was combined with 0.4 ml of D2O and TSP in an NMRtube. Quantitative C-13 and P-31 NMR spectra were taken at 25° C. on aVarian UNITY® 300 MHz NMR using standard suppressed nuclear Overhauserconditions. For P-31 NMR analysis, the samples were first screened forthe presence of phosphorus by obtaining a broad band spectrum, thesamples that contained phosphorus were then quantitatively analyzedafter they were spiked with a known amount of trimethyl phosphate.Corresponding properties of four typical commercialpoly(aminoamide)-epichlorohydrin adhesives designated in Table 1 as PAEH, PAE CT, PAE R, AND PAE C are included for comparison.

TABLE 1 Number Peak Weight Z- Poly- Azetidinium Sample Average Mol. Wt.Average Average dispersity Mol % Charge ID (MN) (Mp) (Mw) (Mz) (Mw/Mn)DETA (meq/g) 378G55 2260 3320 24,400 119,100 10.8 0 0 315D54 1950 341018,100 79,400 9.29 0 0 PAE H 1310 970 90,800 614,300 69.2 2.9 0.11 PAECT 2630 2630 127,300 719,300 48.5 23.8 0.88 PAE R 1720 2450 114,500666,700 66.5 6.3 0.21 PAE C 3000 2650 131,000 689,500 43.6 4.1 0.16

In addition to the advantages in re-wetability provided by phosphoricacid stabilization, the data in Table 1 demonstrates that because 378G55is fully cross-linked, it has developed quite a bit of both dry and wetadhesion. Moreover, it has relatively lower molecular weight than thetypical commercial PAE adhesives (i.e., ⅙ or less in Mz), it has minimalor no charge density, and nondetectable residual azetidinium. As aresult, it is not subject to thermosetting and therefore is much softerthan commercial PAE adhesives when the creping temperature is high. Thebeneficial effect of cross-linking on dry and wet adhesion of the isshown by the dry and wet tack results in Table 2, in which theformulations of Examples 2 (378G55) and 3 (315D54) are compared topartially cross-linked adhesives. It is evident that both high and lowmolecular weight partially cross-linked adhesives did not perform aswell as the fully cross-linked adhesives.

TABLE 2 Ref. Adhesive Backbone Solids pH Acid X-Link Mol. Wt. × 1000 DryTack Wet Tack Rewet 13/A 378G55 Adipic 35 7 Phosphoric Full 90 10 10Dissolves 13/E 315D54 Adipic 35 7 Sulfuric Full 90 7 10 Dissolves7649/58/S 457T20 Adipic 15 7 Sulfuric Full 325 5 7 Swells 13/B 473G03Adipic 15 4 Phosphoric Partial 325 2 2 Swells 13/C 473G05 Adipic 35 7Phosphoric Partial 90 3 2 Slow Swell 13/D 378G95 Glutaric 15 4Phosphoric Partial 250 2 2 Swells 7649/58/M C77 Glutaric 15 4 SulfuricPartial 250 6 3 Dissolves

While both low molecular weight fully cross-linked phosphoric acidquenched adhesive had good wet tack values, the phosphoric acid basedadhesive displayed significantly better dry tack values.

Example 4 Comparing the Phosphoric Acid Stabilized Adhesive to Prior ArtSulfuric Acid Stabilized Crepe Adhesive

The formulations of Examples 2 and 3 were used in runs preparing tissueon a Yankee drum with apparatus in which the carrier fabric did notextend to the entire drive and operator sides, leaving drive andoperator edges exposed. Referring to FIG. 2, the top blade was run withthe sulfuric acid stabilized adhesive of Example 3, while the bottom wasrun with the phosphoric acid stabilized adhesive of Example 2. Eachblade was run for 4 reels, about 80 minutes. As shown in FIG. 2, thephosphoric acid stabilized adhesive did not build a hard coating on theedges of the rear blade surface when a water spray at 20 psi was appliedon the edges of the Yankee surface. Under the same conditions, thesulfuric acid stabilized adhesive built hard coating on both edges ofthe rear blade surface. This demonstrates that the phosphoric acidstabilized adhesive is re-wetable while the sulfuric acid stabilizedadhesive did not exhibit sufficient re-wetability to remove the buildup. This result is quite significant because coating build-up on theedges of the blade can often result in sheet plugging, picking, andscuffing.

Differences between the two adhesives on key physical properties arealso seen in the table of FIG. 4, which shows a comparison of thephysical properties of tissue produced using the phosphoric acidstabilized adhesive of Example 2 (denoted 378G55) as compared to tissueproduced using the sulfuric acid stabilized adhesive of Example 3(denoted 315D54). At high temperatures, 378G55 is more re-wetable than315D54 as indicated by not having significant edge coating build-up ofthe creping blade at the sheet temperature of 257° F. under water edgespray. The 315D54 had quite a bit of coating build-up on the edges ofthe creping blade at 260° F. even under a similar water edge spray.However, the edge coating build-up reduced with 315D54 when the sheettemperature is reduced to 250° F. This improved wet-ability provided aconsiderable improvement in adhesion resulting in a softer sheet asreflected by a significant reduction in base sheet GM Modulus when theadhesive was switched from 315D54 (i.e., GM Modulus of 59 g/%) to 378G55(i.e., GMM of 49.6 g/%) at the sheet temperature close to 260° F.However, when the sheet temperature dropped to 250° F., the base sheetproduced with 315D54 had a GM Modulus (i.e., 47.6 g/%) similar to thatof the based sheet produced with 378G55 at 257° F. sheet temperature. Itis evident that 378G55 performs well at higher sheet temperature while315D54 can only perform as well at lower sheet temperature.

Referring to Samples 18-1 through 21-1 of FIG. 4, adding 2 % of thewetting agent monoammonium phosphate (MAP) to the prior art sulfuricacid quenched adhesive (315D54) did not improve any key base sheetproperties or remove edge coating build-up. Adding MAP to 315D54 resultsin harder coating with less re-wetability and less adhesion. Thisdemonstrates the significant and surprising advantages of stabilizingthe adhesive with phosphoric acid.

Example 5 Comparing the Effectiveness of the Phosphoric Acid StabilizedAdhesive to the Commercial PAE and PVOH Adhesives on Creping Base SheetsComprising AKD

To demonstrate the superior performance obtained with the crepingadhesives of the present invention (Unicrepe PAE), a series of crepingtrials were performed using four different commercially availableconventional creping adhesives based on PAE or PVOH at an add on rate of4 lbs. of creping adhesive per ton of paper passed over Yankee. Crepingwas attempted with two base sheets: a conventional wet strength basesheet for napkin stock which was substantially free of anyrelease/barrier material, and a barrier napkin base sheets comprisingalkenyl ketene dimer in the amounts indicated. All of the crepingadhesives were satisfactory with a conventional base sheet. Only thecreping adhesive of the present invention was suitable for use with basesheets containing 3.25 lbs of alkenyl ketene dimer per ton of tissue.Referring to Table 3, as indicated in the comments column, theconventional creping adhesives resulted in poor creping and unstablesheets. It is believed that this result can be attributed to the verylow creping force observed with each of conventional adhesives.Throughout these examples, a 5° blade bevel was used.

TABLE 3 Creping force AKD Example Creping adhesive (#/12 in.) #/tonComments N-1 Hercules (conventional PAE) 1.0 0 Good creping and sheetstability N-2 ″ 0.3 1.75 Poor creping, heavy deposit on Yankee N-3Unicrepe PAE 1.4 0 Good creping and sheet H₃PO₄ Quenched stability N-4Unicrepe PAE 0.8 3.25 Good creping and sheet H₃PO₄ Quenched stabilityN-5 Solvox 4480 (conventional PAE) 1.4 0 Good creping, good sheetstability N-6 ″ 0.2 3.25 Sheet floated, poor creping N-7 Celvol 540 0.8Zero Good creping and sheet stability N-8 ″ 0.4 3.25 Poor creping, heavydeposit on Yankee N-9 Ultra crepe HT 1 0 Good creping, good sheetstability N-10 ″ 0 3.25 Poor creping, hard surface baked on Yankee

1. A phosphoric acid stabilized poly(aminoamide)-epihalohydrin crepingadhesive.
 2. The adhesive of claim 1 in which thepoly(aminoamide)-epihalohydrin creping adhesive is apoly(aminoamide)-epichlorohydrin adhesive.
 3. The adhesive of claim 1 inwhich the poly(aminoamide)-epihalohydrin creping adhesive is prepared byfirst reacting a dibasic carboxylic acid, or its ester, half-ester, oranhydride derivative, with a polyalkylene polyamine under conditionssuitable to produce a water soluble polyamide, the water-solublepolyamide is then reacted with an epihalohydrin, and stabilized byacidification with phosphoric acid to a pH of 3.5-7.0 at the end of thepolymerization reaction.
 4. The adhesive of claim 3 in which thepoly(aminoamide)-epihalohydrin polymer is stabilized withortho-phosphoric acid.
 5. The adhesive of claim 3 in which thedicarboxylic acid, or its ester, half-ester, or anhydride derivative, isone of a saturated aliphatic dibasic carboxylic acids, ester,half-ester, or anhydride derivative, containing from about 3 to about 10carbon atoms.
 6. The adhesive of claim 3 in which the dicarboxylic acidis adipic acid.
 7. The adhesive of claim 3 in which the epihalohydrinused in preparing the poly(aminoamide)-epihalohydrin polymer isepichlorohydrin.
 8. The adhesive of claim 1 in which the phosphoric acidstabilized poly(aminoamide)-epihalohydrin creping adhesive issubstantially fully cross-linked.
 9. The adhesive of claim 3 in whichthe water-soluble polyamide is reacted with epihalohydrin until thepoly(aminoamide)-epihalohydrin is substantially fully cross-linked. 10.A substantially fully cross-linked phosphoric acid stabilizedpoly(aminoamide)-epichlorohydrin creping adhesive prepared by firstreacting adipic acid with a polyalkylene polyamine under conditionssuitable to produce a water soluble polyamide, the water-solublepolyamide is then reacted with epichlorohydrin until the polymer issubstantially fully cross-linked, and stabilized by acidification withortho-phosphoric acid at the end of the polymerization reaction.
 11. Amethod of preparing a phosphoric acid stabilizedpoly(aminoamide)-epihalohydrin creping adhesive, comprising: firstreacting a dibasic carboxylic acid, or its ester, half-ester, oranhydride derivative, with a polyalkylene polyamine under conditionssuitable to produce a water soluble polyamide; reacting thewater-soluble polyamide with an epihalohydrin; and stabilizing theresultant product at the end of the polymerization reaction byacidification with phosphoric acid to a pH of 3.5-7.0.
 12. The method ofclaim 11 in which the poly(aminoamide)-epihalohydrin polymer isstabilized with ortho-phosphoric acid.
 13. The method of claim 11 inwhich the dicarboxylic acid, or its ester, half-ester, or anhydridederivative, is one of a saturated aliphatic dibasic carboxylic acids,ester, half-ester, or anhydride derivative, containing from about 3 toabout 10 carbon atoms.
 14. The method of claim 11 in which thedicarboxylic acid is adipic acid.
 15. The method of claim 11 in whichthe epihalohydrin used in preparing the poly(aminoamide)-epihalohydrinpolymer is epichlorohydrin.
 16. A method of preparing a substantiallyfully linked phosphoric acid stabilized poly(aminoamide)-epihalohydrincreping adhesive, comprising: first reacting adipic acid, with apolyalkylene polyamine under conditions suitable to produce a watersoluble polyamide; reacting the water-soluble polyamide withepichlorohydrin until the polymer is substantially fully cross-linked;and stabilizing the resultant product at the end of the polymerizationreaction by acidifying the substantially fully cross-linked polymer withortho-phosphoric acid.